Herbst Technik pioneered the concept of cooling ceiling with capillary tubes and changed the way people plan and install air conditioning of buildings. The company's technology introduced an economic and easy way of installing radiant surfaces with integrated capillary tubes for cooling and heating with minimum consumption of space and energy, maximum comfort. The enthalpy changer with the new cross linked capillary tubes - called katubes - will run air conditioning with maximal heat recovery.

Herr K. says: Radiant cooling follows the same principles as radiant heating. The heat transfer occurs between the space and the capillary tubes through a temperature differential. However, like radiant heating, the colder ceiling absorbs the thermal energy radiating from people and their surroundings. The major difference between cooled ceiling and cooling by air is the energy transport mechanism. Cooling by air uses convection only, whereas cooled ceiling uses a combination of radiation and convection. This amount of radiated heat transfer can be as high as fifty five percent, while convection accounts for the remainder. With cold ceilings, the radiated heat transfer occurs through a net emission of electromagnetic waves from the warm occupants and their surroundings to the cool ceiling. On the other hand, convection first cools the room air due to contact with the cold ceiling, creating convection currents within the space which transfers the heat from its source to the ceiling where it is absorbed.

1 Can your system be used in existing Building?

Herr K. says: Yes. In fact this will be better system as it uses very little ceiling space. Capillary mats can be applied to the existing ceiling as it does not has to lower the ceiling. Main supply and return piping can be installed in crown molding or 2 x 4 wall space to avoid any extensive work.

1How long is the service life of the capillary tube system?

Herr K. says: The service life exceeds 50 years under normal operation conditions. Actually one say, that KaRo mats have the lifetime of the buildings because the capillary tubes can not corrode, are dimensioned with high security factors and run on mild temperatures.

Herr K. says: Outdoor air is pre-conditioned and dehumidified by the Dedicated outside Air System unit (D.O.A.S). The building is maintained at a slight positive pressure with respect to the outside to control infiltration of humid air. Once the dehumidified air is in the space, the dew point is monitored and chilled ceiling is controlled to remain above the dew point.

Herr K. says: As it often asked, why put cooling mats in the ceiling? Heat rises, doesn't it? The answer is no, heat does not rise. Warm air rises. The Capillary Tube Mats are placed in the ceiling because heating and cooling is most effective without creating interference to all the objects. Also usually more area is available for Capillary mats.

Herr K. says: This system can be installed in any type of building. This system is best suited for commercial and institutional buildings. With the ventilation system (D.O.A.S.) controlling the humidity of the supply air, a hydronic radiant system can be installed independent of the outside climate.

Herr K. says: A dew point sensor is installed for every cooling circuit. The electrical resistance of this dew point sensor changes as air humidity fluctuates. If the air humidity is too high (risk of reaching dew point), the electrical resistance changes to such a degree that the regulator device triggers a switch signal. This either increased the temperature of the cooling water or breaks the cooling water circuit, depending on the characteristics of the regulator. Once the dew point danger has passed, the electrical resistance changes again to such an extent that the regulator device re-enables the cooling water circuit.

Herr K. says: Despite their thinness, Capillary mats have a very little loss of pressure. The water in Capillary Tube system runs through many parallel tubes rather than running through just one tube, as compared to thick tubes. The average velocity through capillary tubes is only 10 to 20 cm/second, thus the pressure drop is very low. The velocity in the capillary tubes is always laminar. The tubes are tested at a pressure of 20 bar.

Herr K. says: Capillary tubes are made of polypropylene material. All fittings are also made out of the same material. All pipes and fittings are fused togather in the field, so soldering is not required. Because the Capillary tubes are only 1/16" thick and spaced about 1/8 inch apart, thus the cooling and heating is even. Our capillary tubes have been proven very successful in an European market.

Herr K. says: Yes, all KaRo distributers provide cost estimate for radiant cooling. Any additional service required will be provided based on customer requirements in cooperation with your architect and civil engineer.

Herr K. says: Indoor air quality improves as cooling and heating by Capillary Tube systems incorporates dedicated Outside Air System. This is 100% outside air with no re-circulation of indoor air, thus spreading of odors and other airborne contaminants is avoided.

Herr K. says: Capillary System is fast reacting. After just a few minutes, the Capillay ceiling begins to cool the room effectively. This is brought about by the very small amount of water in the capillary tubes and the positioning of the Capillary Mats close to the surface. In addition, Capillary Tube ceiling is able to regulate itself quite well.

Herr K. says: The radiant heating and cooling with capillary tube - the green house Walter in Berlin, Germany - is running since 1982. Radiant Cooling with capillary Tubes is now State-of-the-art in Europe and Canada. The Olympic village in Vancouver for example has Radiant Heating and Cooling with some 80.000 m2 of KaRo Ceiling → Booklet_Energy.

Herr K. says: Leaking pipes or fittings are not a problem. It is very simple to repair the leaks. First run the water through the mats in order to see a wet spot on the drywall or plaster. Open this damaged areas, than fused the piping on both sides. This will not affect the capacity for cooling or heating.

Herr K. says: None. Pipes and fittings are made out of polypropylene (plastic). Also heating water is at a low temperature - around 90 F (32 ℃) for heating and 60 F (16 ℃) for cooling - so corrosion and oxidation does not take place.

Herr K. says: A pressure and safety test of the system is performed once the installation of the KaRo system has been completed. The test checks whether the KaRo system is installed correctly and completely pressure-tight. Pressure testing is initially performed using an air pressure of 10 bar, thereafter with a water pressure of 10 bar.

Herr K. says: A damaged capillary tube presents no problem and can be rectified without any great overhead or expense. The capillary tube is separated off at the damaged area and both ends of the capillary tube are welded up (isolated). There is no longer any energy exchange along this capillary tube, but this is not noticeable within the total cooling capacity.

Herr K. says: Thermal energy can be transported through pipes with little pump power, saving approximately 70 to 80% of the fan power normally used to condition the building. This alone reduces the peak-power of the air conditioning system by about 30 to 45%. See www.doas.psu.edu

Herr K. says: Although the cost associated with the material and labor may be slightly higher than the forced air system, there are other significant savings that should be taken into consideration. Due to reduction in the air volume, the size of the ductwork is greatly reduced. This means that plenum height could be reduced by approximately one foot per floor. The reduction in plenum height can be translated into a reduction in overall building height, thus reducing the construction cost of the building.

Herr K. says: The chilled ceiling can provide capacity up to 30 btu/sq.ft (100 W/m2) in combination wih ventilation. This capacity is generally sufficient if the project is designed based on green energy concepts. Most architects are familiar with green energy design.

01 My God, these thin tubes, I doubt that this will work. They will be blocked within day! The capillary tubes, don`t they get blocked by dirty water?

Herr K. says: Any drinking water is good for KaRo. There is no special water treatment necessary because of the outstanding corrosion resistance of the polypropylene, used for KaRo. Normally there are two possible reasons for a water system: Calcium deposition or corrosion particles.Calcium Considerable calcium deposition is not possible at KaRo, because it is a cycle system like in the car for the motor. Always the same water is circulating and no new calcium is coming from outside.Corrosion There is no corrosion at KaRo because the KaRo mats and all the piping and armatures in the KaRo water circuit are of corrosion resistant material.

Herr K. says: If there is a leak in a capillary tube the damage is only limited. Water will only drain from the damaged capillary tube until pressure equalization with the environment is reached. For this reason the maximum possible amount of leakage is determined by the size of the expansion tank, which has normally just a few liters. Repairs are easily done by atrophying the damaged capillary tubes with the welding tool or iron. The reduction of the active area is hardly noticeable because of the big number of capillary tubes.

Herr K. says: Ductwork of air conditioning plants often dictate the height of the floors and the space requirement for technical equipment. Conventional air conditioning plants need big amount of supply air, because they do the cooling with air only. High cooling load needs high volume of air. KaRo is transporting the heat with water, that need less then one thousandth of the volume of air, to transport the same amount of heat. How can KaRo ceilings have such a high cooling capacity wit mild water temperatures only? The cooling load in the rooms have a relative high surface temperature. Our skin or example has a medium temperature of 32 °C. With a temperature of 16 °C on the surface of the KaRo ceiling you have a temperature difference of 16 degree for the transport of the heat. Computer and light have even higher temperatures.

04 We are located in the Atlanta, Georgia area. Due to the high humidity in our area would this system be practical and if so, could it be adapted for residential use?

Herr K. says: The only limitation for the cooling of the KaRo ceiling is the dew point of the room air. In humid regions it is a must to combine the KaRo ceiling with a little air conditioning plant for an air volume of 1 to 2 changes of air volume per hour. The air conditioning plant is bringing the dew point of the air down to 12 to 14 C, a temperature the KaRo ceiling will work fine. For security reasons there is a sensor or a window switch, that turns off the cooling, if you open the window at high humidity of the outside air.

In Europe more than 80% of the KaRo ceilings are installed in office buildings. But of course the advantage of no noise, no draft and little energy consumption is also enjoined in residential houses.

05 How can KaRo ceilings have such a high cooling capacity with mild water temperatures only?

Herr K. says: The cooling load in the rooms have a relative high surface temperature. Our skin or example has a medium temperature of 32 °C. With a temperature of 16 °C on the surface of the KaRo ceiling you have a temperature difference of 16 degree for the transport of the heat. Computer and light have even higher temperatures.

Herr K. says: For using radiant ceiling for cooling you need a very high thermal efficiency. Because the cooling capacity is limited – different to heating - limited by the dew-point this in turn is limited by the lowest temperature in the ceiling. Tick pipe systems therefore are not suitable for that purpose.KaRo mats embedded in plaster for example have a thermal effectiveness of over 98%. This means that if a layer of water were underneath the plaster instead of the capillary tubes, a construction impossibility, it could only be less than two percent more effective.

Herr K. says: No. It was Donald Herbst, the inventor of the KaRo system, who named in the 80th the small pipes of the system “capillary tubes”, to find a clear description compared with the thick pipe systems.Now this expression is generally used in Europe in technical literature as well as in the colloquium speech. The German word for capillary tube is “Kapillar Rohr”, that has given KaRo the name.

Herr K. says: Yes. For getting a comfort room climate, you dehumidify the supply in conventional air conditioning plants. With that you have a normal dew point inside and can use the KaRo ceiling like in regions, that have lower humidity.The control system switches off the cooling, if the inside humidity gets up, for example because windows where opened.

09 What is the pressure loss of the capillary mats of the KaRo system?

Herr K. says: Despite their thinness, KaRo mats have a very little loss of pressure. The water in a KaRo system runs through many parallel capillary tubes, rather than running through just one tube, as in a system with thick tubes. The typical velocity of flow with KaRo averages only 10 to 20 cm/second. The velocity in the capillary tubes is always laminar. That has the positive side effect that the loss of pressure in the KaRo mats grows only linear with the amount of extra water, and not quadratic.

Herr K. says: “KaRo cooling can be switched on like a light.” This is the feeling you get if you first turn on the KaRo ceiling in the middle of a warm day. After just a few minutes, the KaRo ceiling begins to cool the room effectively. This is brought about by the very small amount of water in the capillary tubes and the positioning of the mats closely to the surface. In addition, the KaRo ceiling is able to regulate itself quite well.

Herr K. says: For the dew point protection there are 2 possible strategies:Dew point sensorsThe dew point is monitored at the coldest point on the cooling ceiling. If the dew point is reached the cooling is reduced, either with the closing of the control valves, the switching off of the pump, or the raising of the supply water temperature. Window switchesEach window which can be opened receives a window switch, which automatically turns off the cooling if a window is opened.

12 Steve: We are working on Children’s and Women’s Mental Hospital. Our design temp for outdoors is 85F DB and 67F WB. Do we need a chiller for the air?

Herr K. says: With any air conditioning system you would need to dry the fresh air of 67 ºF (= 19,4 ºC ) to get a comfort ambient. For a room temperature of 22 ºC and 70 % r.h. for example, the supply air should be dried down to a water content of about 10 g/kg corresponding to a WB of 14 ºC (57 ºF).

If room temperature is 24 ºC the WB temperature of the supply air can be 16 ºC (60 ºF).

The advantage with KaRo is that only a very little amount of air has to be dried. The fresh air rate in for hospitals with KaRo has to be only about 4 m3/h m2 or 20 m3/h person (0,22 cfm/sq ft or 12 cfm/person) reducing to 50% at extreme hot or cold days.

Herr K. says: The temperature difference between hot and cold side of the chillers determine their efficiency. The KaRo ceiling needs only mild temperatures and the ventilation the more expensive lower water temperatures for the dehumidification of the air.

In any case cooling with the KaRo ceiling is the most economic way. Therefore:

In big buildings the chillers are separated into 2 systems: • Low temperature for the ventilation and mild temperature for KaRo Ceiling.

In smaller installation one chiller can be used with the chilled water first passing the air cooler before going the KaRo Ceiling.